The German laid open print 26 46 358 discloses a filter device in which the hollow-fiber bundle encloses a central conduit in a ring-like manner, and the ends of the ring-shaped hollow-fiber bundle are sealed off by a molding compound both with respect to the central conduit and with respect to the housing casing concentrically enclosing it.
Another known filter device likewise comprises a tubular housing which encloses the hollow-fiber bundle, the ends of the hollow-fiber bundle being joined to the ends of the tubular housing by a molding compound. In this filter device, the housing is provided in each case with radial connection pieces, adjacent to the molding compounds, which form the inlets and outlets to the second flow space. The capillary tubes of the hollow-fiber bundle enclosed by the molding compounds are cut at their end faces to open them. Caps provided with connection pieces which form the inlets and outlets of the first flow space are then placed sealingly on the ends of the tubular casing.
These known filter devices are used, for example, as capillary dialyzers, the flow spaces formed by the capillary-tube passages forming the blood chamber, and the housing enclosing the hollow-fiber bundle forming the dialysate chamber in which the dialysate flows around the hollow fibers.
The problem existing in the known filter devices is that the molding compound, usually made of PU [polyurethane fiber], which hardens in a disk shape and forms a sealing between the two flow spaces, shrinks when hardening, so that stresses develop in the disk-shaped sealings formed by the molding compounds which can lead to cracks and even detachments of the molding compounds from the housing casing enclosing them. As a result, the two flow spaces are no longer completely sealed off from one another, and the adhesion of the sealing compounds to the housing enclosing the fiber bundle, said adhesion producing the seal, is no longer reliably assured.
In a filter device of the type indicated at the outset disclosed by EP 0 305 687 B1, the disk-shaped molding compounds are enclosed by interposed rings to which the molding compounds do not adhere, so that they can shrink free of stress. This stress-free shrinking prevents cracks in the disk-shaped molding compounds, and makes it possible to dispense with a direct sealing between the peripheral edge of the sealing compounds and the housing enclosing them. To nevertheless maintain a sealing between the two flow spaces, the first space is sealed off by caps placed on the molding compound, and specifically by sealing devices which run over the edge area of the molding compound and against which the caps are pressed.
In this known filter device, the problem now exists of producing a connection to the second space formed by the housing enclosing the fiber bundle. This connection is produced in the known filter device, in that the diameter of the tubular housing is widened at its end areas more or less in the manner of a sleeve, these widened areas being provided with radial connection pieces. These connection pieces open through into the second space formed by the housing, the widened sections of the housing being sealed off from the first space because the caps are sealingly joined to the widened sections, so that a sealing is produced to the outside by the cap edge, and a sealing is produced with respect to the first space by the circumferential sealing ring. This type of arrangement of the connection pieces at the second space formed by the housing is relatively costly. Furthermore, dead spaces which are poorly rinsed develop above or below the connection pieces, at which gas bubbles can collect. This can have a disadvantageous effect during disinfecting or sterilization, as well as generally when handling.